Regex Injection

Regex injection is a technique where attackers manipulate regular expressions to exploit vulnerabilities on websites. In this article, we will explore the concept of regex injection and its implications on the popular website, pwn.guide. Let's dive into this intriguing topic with some examples.

What is Regex Injection?

Regex injection occurs when attackers use specially crafted regular expressions to bypass filters and compromise a website's functionality. It takes advantage of the fact that regular expressions are used to validate and filter user inputs on many websites.

An Example of Regex Injection

To understand regex injection, let's imagine that pwn.guide has a search feature that uses regex to filter user inputs. The regex pattern used for filtering allows only alphabetic characters and spaces in the search query, with a maximum length of 20 characters. It might look something like this:

^[a-zA-Z\s]{1,20}$

Now, suppose an attacker wants to inject a malicious regex pattern to bypass this filter. They could inject the following pattern:

^.*$

This injection effectively bypasses the filter and allows any input, regardless of the length or characters used. It can lead to abuse of the search feature or potential security vulnerabilities.

The Consequences of Regex Injection

Regex injection can have serious consequences for a website:

• Data Leakage: Attackers can exploit regex injection to retrieve sensitive data that wasn't intended for public view.

• Arbitrary Code Execution: By injecting malicious regex patterns, attackers may execute arbitrary code on the server, compromising its security.

• Denial of Service: Repeated injection attempts can overload the website, causing it to become unresponsive to legitimate users.